BandgapEngineering

Bandgap engineering is the design and manipulation of a material's electronic bandgap to tailor its optical and electronic properties for specific applications. It is central to semiconductor physics and optoelectronics because the bandgap sets absorption and emission wavelengths, carrier confinement, and device efficiency.

The main strategies are alloying, quantum confinement, strain, and heterostructuring. Alloying changes the bandgap by mixing constituent materials, with the composition dependence often described by a bowing parameter to account for nonlinearity. Quantum confinement in low-dimensional structures such as quantum wells, wires, and dots increases the effective bandgap as dimensions shrink, enabling blue-shifts and enhanced radiative rates. Strain engineering uses lattice mismatch between adjacent layers to modify band edges and effective masses, enabling bandgap tuning and improved carrier transport in heterostructures. Heterostructures and superlattices create abrupt band offsets that localize carriers and tailor absorption and emission spectra.

Applications span light-emitting diodes, laser diodes, photodetectors, solar cells, and high-speed electronics. In solar cells and photovoltaics, stacking materials with different bandgaps in tandem configurations maximizes spectrum utilization. Material systems include III–V semiconductors such as GaAs and InP, II–VI systems, perovskites, and emerging two-dimensional materials. Challenges include defects, strain relaxation, lattice-matching constraints, and thermal stability; precise growth requires epitaxial techniques such as molecular beam epitaxy, metal-organic chemical vapor deposition, or chemical vapor deposition.